As an aluminum oxycarbide, the following two types: Al2OC and Al4O4C, have been known. In particular, Al4O4C is characterized by high-temperature stability, anti-oxidation effect, excellent corrosion resistance, and low thermal expansion coefficient. It is expected as a refractory or ceramic material or a raw material therefor, in the future. Especially, Al4O4C is expected as a raw material for a carbon-containing refractory material, such as an alumina-carbon based refractory material or a magnesia-carbon based refractory material, used as a refractory material for use with molten metal such as molten iron or steel.
As a method of producing an aluminum oxycarbide composition containing such Al4O4C (aluminum oxycarbide), the following Non-Patent Document 1 discloses a method in which alumina and graphite are subjected to a heat treatment in an argon atmosphere. Specifically, after adding ethanol to alumina having an average particle size of 0.1 μm, and graphite reagent having a particle size of 45 μm or less, they are mixed together in an agate mortar, and then dried. A powder (2 g) of the mixture is put into a graphite crucible, and burnt at 1700° C. in a preliminarily evacuated electric furnace, while supplying argon gas thereinto. The following Non-Patent Document 2 discloses a method of producing an aluminum oxycarbide composition using an arc furnace. However, the Non-Patent Document 2 mentions that, along with an increase in amount of carbon in the aluminum oxycarbide composition obtained by the disclosed production method, Al4C3 reactive with water is formed in a larger amount.
On the other hand, the following Patent Document 1 discloses a technique for suppressing the formation of Al4C3, wherein a carbon-based raw material and alumina are homogeneously mixed together to eliminate a dispersion in C component.
However, it is known that in ambient atmosphere, Al4O4C is oxidized at about 850° C. and transformed into alumina. Particularly, in cases where Al4O4C having fine crystal grains is used as a raw material for a refractory material, it will be oxidized. Thus, it is difficult to maintain the advantageous effects such as oxidation resistance, corrosion resistance and low thermal expansion coefficient, for a long time.